Fierce fighting continued overnight in Eastern Ukraine on the Russian border. A new U.N. report says, the violence there has killed more than 1,100 people since mid-April. Russia's foreign minister rejected U.S. claims that his country has been supporting the pro-Russian fighters there. Sergei Lavrov also dismissed the threat of tougher Western sanctions.

NPR's Corey Flintoff joins us now from Moscow. And Corey, let's start with that latest U.N. report - a very high death toll, more than a thousand people killed and many more wounded. What else did that report have to say?

COREY FLINTOFF, BYLINE: Renee, the U.N.'s High Commissioner for Human Rights Navi Pillay pointed out that the fighting is now getting more intense in these densely populated cities like Donetsk and Lugansk, and that's alarming because of the danger of harming more civilians. She also said that the shooting down of the Malaysian airliner on July 17 may constitute a war crime.

MONTAGNE: Well, on the subject of the fighting; yesterday the State Department released satellite images it said showed that Russian troops had been firing rockets from Russia into Ukraine. You've seen those photographs. What did you see?

FLINTOFF: Well, there are close-ups of two areas, one on each side of the border. And on the Russian side of the border, you can see a field with what appears to be a row of burn marks, big burn marks. And the State Department says, those are marks where rocket launchers were deployed, and those burn marks come from the flames that the rockets were fired. The second close-up follows the trajectory of those rockets and it shows a field in Ukraine that's covered with what looked like hundreds of shell craters, and that field was a staging area for Ukrainian troops. So if this is true, then it would be proof that Russia is now directly taking part in this war.

MONTAGNE: And Russia, what did it have to say?

FLINTOFF: Well, the foreign minister, Sergei Lavrov, gave a big news conference this morning and he basically sought to cast doubt on everything that the United States has presented as evidence so far. He didn't respond to the specifics of these latest photographs, but he behaved basically as if the United States hasn't presented any credible proof that Russia's been involved. Actually, a lot of today's news conference focused on the threat of further sanctions against Russia, you know, which suggest that Moscow may be anticipating that those sanctions are finally on the way. Lavrov said that the sanctions will only make Russia's economy more self-sufficient. Well, here he is talking through a translator.

SERGEI LAVROV: (Through translator) I'd like to assure you that Russia will prevail. Russia will overcome the difficulties in the economy, maybe we'll become more confident, more independent.

FLINTOFF: That seems to be very much in keeping with the Kremlin's attitude these days. You know, the belief that Russia can actually ride out the sanctions, and sanctions could even help the country's manufacturing sector because people will turn to domestically made products instead of imports.

MONTAGNE: And Corey, let's get back to that Malaysia Airlines plane that was shot down. As you just said, the U.N. commissioner for human rights says it may be a war crime. And we know investigators have had trouble getting into the site of the debris. What can you tell us about that?

FLINTOFF: Well, for the second day in a row, police and experts from the Netherlands and Australia tried to get out to the wreckage site today and they had to turn back. The Organization for Security and Cooperation in Europe said a convoy of about 20 cars was on its way out to the site. They reached a town that was not far away but they heard the sounds of heavy shelling and saw residents fleeing. So once again, they were forced to turn back.

You know, this is a risky proposition for these countries. They have to be concerned that their police could be caught in a crossfire, and this fighting is just now constant in Donetsk and the area around it. And there's also the fear that the Separatists could use the police and experts as hostages. They've taken observers hostage in the past and held them for weeks. And if they get desperate that could happen again. If Russia is in fact shelling across the border, there's also the danger that the investigators could be caught in that.